Thin Firm Transistor Liquid Crystal Displays (TFT-LCDs) become dominant products because of their advantages of small volume, low power consumption, no radiation and high resolution.
A TFT-LCD is constituted mainly by assembling an array substrate and a color filter substrate, wherein a plurality of gate scanning lines and a plurality of data signal lines crossing one another are formed on the array substrate, and a plurality of pixel regions are defined by the plurality of gate scanning lines and the plurality of data signal lines and arranged in a matrix, each of the plurality of pixel regions covered with a pixel electrode. As shown in FIG. 1, the TFT-LCD array substrate comprises: a plurality of gate scanning lines 100 and a plurality of data signal lines 200, crossing one another; a plurality of pixel regions, defined by the plurality of gate scanning lines 100 and the plurality of data signal lines 200 and arranged in a matrix; and pixel electrodes 300, covering each of the plurality of pixel regions, wherein each of the plurality of pixel regions is defined by two adjacent gate scanning lines 100 and two adjacent data signal lines 200 crossing with each other.
Since the pixel electrode covering each of the pixel regions does not cover the corresponding gate scanning line and the corresponding data signal line, there is light leakage in the regions where the gate scanning line and the data signal line are located; thus, a black matrix (BM) is needed to be provided at corresponding positions on the color filter substrate, which therefore adversely affects the aperture ratio of TFT-LCD.
At present, the resolution of the LCD is continuously improved, with increased pixels per inch (PPI) and smaller pixel size. For a high-level pixel design, improvement of the aperture ratio is particularly important, but is also increasingly difficult.
In general, main factors affecting the aperture ration of the TFT-LCD comprise:
1. the resolution and display size of the LCD. Because the resolution and display size determine a pixel size, and on the basis of a current process, the larger the pixel size is, the higher the aperture ratio relatively is;
2. a electrode material, the resistivity of the gate scanning line and the data signal line is a focus of the attention; if the electrode material has a high resistivity, then, in order to reduce signal transmission delay, these lines have to be manufactured with a relatively larger width, which undoubtedly may reduce the aperture ratio of the pixel;
3. a design margin or a process margin: in order to obtain a stable yield, it is necessary to ensure the stable and reliable design; in addition, taking into account the process fluctuation, a certain margin will be kept, which also may affect the aperture ratio of the pixel.
For a specific TFT-LCD product, after the resolution and size are determined, the pixel size is also fixed. Moreover, although there are metallic materials with a relatively low resistivity among existing available electrode materials, due to a process, a line-width can not be manufactured to be relatively small. Therefore, reducing the design margin and the process margin becomes a major way to improve the aperture ratio.
For example, in some present TFT-LCD products, a pixel electrode is covered above the data signal line, thus a light leakage area is reduced; in addition, the data signal line can be utilized to block light, so that a width of the BM can be reduced, and thus the aperture ratio is improved.
However, a width of the data signal line is relatively narrow, typically about 4 microns; in order to prevent short circuit from occurring between adjacent pixel electrodes, in these TFT-LCD products, the pixel electrodes can covered only above a part of the data signal lines or a part of the regions above the data signal lines, that is, there still exist gap between adjacent pixel electrodes. Thus, many regions on the array substrate do not covered with the pixel electrodes, and therefore, a modulated electric field can not be formed in such regions, thus the light leakage still exists in the liquid crystal display, and the BM is still needed to be provided at corresponding positions on the color filter substrate. In this way, the aperture ratio of the TFT-LCD can only be improved limitedly; moreover, the risk of short circuit exists. Therefore, the stability and aperture ratio of the existing TFT-LCD are still needed to be further improved.